In the prior art, patent document 1 discloses an example of a semiconductor device, or semiconductor module, including a circuit substrate formed by joining a metal plate of pure aluminum or the like on the two opposite surfaces of a ceramic substrate, or insulative substrate, of aluminum nitride or the like. A heat dissipation device, that is, a heat sink, is joined with the circuit substrate to form a module. In this type of semiconductor device, the heat generated by the semiconductor element is dissipated by the heat dissipation device.